Method and apparatus for bending sheet material



Aug. 14, 1945. w. H. NOBLES 2,382,807

METHOD AND APPARATUS FOR BENDING SHEET MATERIAL Filed Sept. 21', 1942 3 Sheets-Shget l 'Wa/z/um/ b. NOIEZZA/ INVENTOR BY mfgunm n ATTORNEY &

Aug. 14, 1945. I w NQBLES 2,382,807

METHOD AND APPARATUS FOR BENDING SHEET MATERIAL Filed Sept. 21, 1942 5 Sheets-Sheet 2 INVENTOR ATTORNEY BY unng Aug. 14, 1945. w. H. NOBLE S I 2,382,807

METHOD AND APPARATUS FOR BENDING SHEET MATERIAL I Filed Sept. 21, 1942 3 Sheets-Sheqt 3 61 Wal/z/wn/fi. 11 m 7 INVENTOR Y MP6 ATTORNEY bend during the bending the material.

Patented Aug. 14, 1945 METHOD AND APPARATUS FOR BENDING SHEET MATERIAL Warren H. Nobles, St. Paul, Minn., assig'nor to Seeger Refrigerator Company, St. Paul, Minn., a corporation of Minnesota Application September 21, 1942, Serial No. 459,194

12 Claims.

My invention relates to an improvement in method and apparatus for bending sheet material, whereln it is desired to provide an efllcient means of bending materials which are diflicult to bend smoothly.

In the past it has been difllcult to bend'materials such as composition board, of which the product commercially known as Masonite is an example. Because of the present shortage of metal sheets, it has been increasingly desirable to substitute composition board for metal in constructions in which it is necessary to bend such materials out of their normal fiat condition. While relatively large radius bends have previously been made in this material, it was thought impossible to bend the material on a relatively small radius without fracturing the outer surface of the material at the point of bend.

Furthermore, in the bendingor' this" material it has been recommended that the Masonite sheets be soaked in liquid for a considerable number of hours prior to the bending operation. This causes the boards to absorb a certain amount of water to prevent the board from breaking at the point of bend by rendering the board less brittle. This soaking process has made the bending of the composition material a dimcult production problem.

It is the object of the present invention to provide an apparatus capable of bending sheet material about a relatively small radius without fracturing the outer surface of the material at the point of bend. This result is accomplished through the use of a flexible draw sheet which extends over the material at the point of bend and which holds the material firmly in place during the bending operation, so that the fibers of the material can not fracture and tear away from the .main body of the material at the point of This flexible draw sheet acts to draw the sheet to be bent over a suitable mandrel, thus bending the sheet to a predetermined shape.

An important feature of the present invention lies in the fact that the use of the flexible draw sheet makes it possible to bend sheet material over a mandrel which is not continuously curved, and which is not provided with an arcuate surface. With my bending apparatus, it is possible to form the material over virtually any mandrel surface which contains no concave portions. The draw sheet will clamp the material to be bent against the surface of the mandrel regardless of whether or not the mandrel is provided with a continuously arcuate surface, wrapping the sheet material over the mandrel surface.

An important feature of the present invention lies in the manner of supporting the draw sheet during the bending operation. In preferred form one end of the flexible draw sheet is anchored to the apparatus frame at a point forwardly from the point of bend, and the other end of the draw sheet is connected by resilient means to a supporting frame. This frame is pivotally secured to the apparatus frame in such a manner that the spring pressure increases as the bend is formed. Thus the pressure on the draw sheet, tending to hold the sheet being bent against the mandrel, increases progressively as the bend is made. Thus the proper pressure to accomplish the desired result is always available at any point of the bend.

A further feature of the present invention lies in the fact that the flexible sheet bears against the sheet material being bent at the point of bend. If this sheet material is a fibrous material, such as Masonite, this arrangement prevents the fibers of the material from standing up or splitting away from the body of the material as the sheet is bent so that the surface of the finished bend is as hard or harder than the rest of the surface.

A further feature of the present invention lies in the fact that no relative movement takes place between the flexible draw sheet and the material to be bent. At the start of the bending operation the flexible draw sheet lies flat upon the surface of the sheet material to be bent, and this flexible sheet continuously bears against the same area of the sheet material during the formation of the bend.

A further feature of the present invention lies in the use of a method which will permit fibrous material, such as Masonite, to absorb the necessary amount of moisture in a short period of time to render the finished product sufficiently pliable to bend without cracking. As a result the necessity of providing huge tanks in which sheet material can be soaked for a number of hours is obviated. In accomplishing this method I heat the liquid in which the Masonite is soaked. This permits penetration of the moisture into the sheet material in an extremely short period of time, making it possible to employ a single heated tank in which the sheet material may be placed for a short period of time immediately prior to the bending operation. This step acts not only to decrease the soaking time of the material, but also acts to preheat the material so that this material need not be maintained on the heated bending mandrel for so long a period in order to properly bend the same.

These and other objects and novel features of my invention will be more clearly and fully set forth in the following specification and claims.

In the drawings forming a part of my specification:

Figure 1 is a side elevational view. partly in section, showing a multiple bending apparatus capable of making two parallel bends at the same time in the sheet material to be bent.

Figure 2 is a top plan view, partly in section, of the apparatus shown in Figure 1.

Figure 3 is an end view of the bending machine shown in Figures 1 and 2.

Figure 4 is a diagrammatic view showing a mandrel, the flexible draw sheet, and a thickness of sheet material to be bent.

Figure 5 is a view similar to Figure 4 showing the flexible draw sheet bent over the mandrel.

Figure 6 is a sectional view through a portion of the bending machine illustrating the frame supporting the flexible draw sheet, as it appears before the start of the bending operation.

Figure 7 is a view similar tovFigure 6 during the bending operation.

Figure 8 is a detailed view of a piece of compostion board showing one manner of assisting the bending operation. I

The bending machine A comprises a frame including a pair of longitudinally extending base channels l extending in parallel relation along the floor. Angular iron legs ll extend upwardly from the ends of the channels III and the upper extremities of the legs H are connected by header channels I2. These channels are bolted or otherwise aiflxed connecting the pairs of legs II, and transversely extending angles l3 extend between the pairs of legs H to complete a substantially rectangular frame.

Extending in vertical relationship, parallel to the legs I I I provide channel uprights i4 arranged in oppositely disposed pairs. Each of the channel uprights I4 is connected at its lower extremity, such as by bolts l5, to the longitudinally extending base channels III, the bolts l extending through elongated slots IS in the channels Hi. The two upright channels of each pair are connected by a transversely extending angle while similar angles I9 connect the base channels l5 to hold these base channels in proper spaced relation. Angles 2|! connect the angles IT, as best illustrated in Figures 1, 2, and 3 of the drawings, and as shown in Figure 2 these angles 20 are provided with elongated slots 2| therein, through which the fastening bolts 22 extend so that the distance between the uprights |4 may be readily adjusted.

As best shown in Figures 1 and 3 of the drawings a mandrel assembly 24 is mounted between a pair of channel-shaped slides 25 which are designed to Slide vertically upon the uprights l4. These slides 25, as shown in Figure 2, are provided with side flanges 26 designed to embrace the sides of the channel l4 so as to form a guide for the vertical sliding of the mandrel assembly 24. The mandrel assembly 24 is of such a width that the guides 25 are held engaged with the uprights.

The mandrel assembly 24 may vary according to the particular construction of any desired machine and in accordance with the material to be bent. In the construction shown the mandrel includes a curved surface plate 21 which may be if any convex shape, but which is shown as havng an arcuate bend of slightly more than ninety assasov degrees. This plate .21 forms the surface over which the sheet material is bent. Furthermore in the mandrel shown, I provide a gas burner 2! which is supported by a gas burner bracket II at each end 3| of the mandrel assembly for the purpose of heating the mandrel plate 21 to the required temperature.

In order to permit insertion and removal of the bent sheet material I mount the mandrel assembly 24 so that it may reciprocate vertically upon the uprights l4. To accomplish this result I provide a transversely extending shaft 22 extending between the uprights [4 of each pair and provide an arm 3! on each shaft 32 near each end thereof arranged to rotate with the shaft 32. A link 34 pivotally connects each arm 32 to an ear 3' projecting downwardly from the slide or guide 25. The link 34 is pivoted at 38 to the ear ll and is pivoted at 31 to the arm 33. The link 34 is adjustable in length as may be seen, the link com prising end sockets and. a central right and left hand threaded bolt engageable therebetween,

It will be noted that an operating lever I! is provided on each shaft 32 for rotating the shaft. When the lever 39 is in the upright position 11- lustrated the link 84 and the arm 33 are in alignment and the mandrel assembly 24 is in its uppermost position, the height of which is regulated by regulating the length of the links 34. However, when the lever 39 is pivoted the shaft I2 is rotated and the link 34 assumes an angular relation with the arm 33, drawing the slide 2| down- ;rardly and thus lowering the mandrel assembly A pair of bending arm supports is mounted on each of the headers l2 for lidable movement thereupon. The bending arm supports 40 comprise channel-shaped brackets designed to engage over the top and bottom edges of the channels l2 and are held to the channels l2 by means of bolts 4|. The bolts 4| extend through slots 42 in the channels l2 and therefore permit longitudinal movement or longitudinal adjustment of the bending arm supports 40. A pair of arms 43 is pivoted at 44 to the bending arm supports 40, one of the arms 43 being pivoted to each bending arm support 40. An angle iron connecting member 45 connects the opposed arms ll of each pair as best illustrated in Figures 6 and 7 of the drawings. A substantially U-shaped frame is thus provided which is pivotally connected at the free ends of the arms to the adjustable bending arm supp rts 40. This frame is arranged to support the free end of the flexible draw sheet, as will now be described.

A T iron connecting member 46 connects opposed bending arm supports 40 of each pair. A

.flat plate 41 is secured to the lower extremity of the T member 45. A flexible draw sheet 49 is terminally connected to an edge of the plate 41 by means of a clamping bar 50, which is held in place. by cap screws 5| or other suitable means. One edge of the flexible draw sheet 49 is thus securely anchored in fixed relation to the bending arm support 40.

The other edge of the substantially rectangular draw sheet 49 is folded over an edge of the T iron 52 and is held in place by a clamping bar 53 secured to the T iron 52 by cap screws or bolts 54. The. T iron 52 is secured at each end to a carriage 55 which is mounted upon rollers 56. The rollers 56 ride in a groove 51 extending longitudinally along each of the arms 43. Thus one end of the draw sheet 49 is anchored between the fixed supports 40 while the other end there- 2,882,807 of is adjustably supported by the U-shaped frame including the arms 43 and the angle iron 46.

An angle iron I. is supported by bearing blocks 60 at each end thereof which are slidable in the rooves 61 formed in the arms 4!. Cap screws 6| extend through the angle 46 or into the bearing blocks to for adjusting the position of the angle '6! with respect to the angle 45. A series of springs 62 connect the clamping plate I! on the T iron 62 with the angle 66 so as to resiliently draw the carriage 66 toward the end of the U-shaped frame. In other words, the flexible draw sheet 49 is stretched and maintained under tension by the springs 62 and the tension of entire bending operation. Therefore the surface of the material bent is not injured by relative movement between this material and the draw'sheet.

I have found my machine particularly desirable for the bending of composition material, such as that commonly known as Masonite. I have found that my machine will bend this material about a relatively small radius without inluring the surface of the material in any way whatsoever. In the bending of material, such as Masonite, the mandrel plate 21 is preferably heated, the temperature of the mandrel being 1 maintained below the scorching point of the mathese springs may be adjusted by means of the cap screws 6 I.

Any means may be provided for pivoting the U- shaped frame includin the arms 43, with respect to the bending arm supports. I have illustrated a pair of slide guides 63 secured to and projecting upwardly from the bending arm supports 46 to support a vertically slidable cross head 64. This cross head 64 may be vertically reciprocated by means of a pneumatic or hydraulic cylinder 85, a-portion of which is shown in Figure 1 of the drawings. A link 66 which is adjustable in length is pivotally connected at 61 to the cross terial. It is preferable to heat the mandrel to a point close to the scorching point of the material being bent, but this temperature is not critical and it is possible to bend the composition at a somewhat lower temperature. In such a case.

however, the bending operation ordinarily requires a greater amount of time.

In thebending of composition such as that described, it has been common practice to soak'the material in liquid for aconslderable period of hours before the bending operation in order to absorb a certain amount of liquid to make'the sheet somewhat more pliable-and to prevent cracking of'the sheet during the bending operahead 64 and is pivotally connected at 6,! to a bending arm 43. Thus by operation of the pistons within the cylinders 66, the links 66 will operate to pivot the arms 43 downwardly at any adjusted speed. I

The operation of the bending machine A is substantially as follows: The lever 39 is operated to pivot the arms 33 to lower the slide guides 25 and the mandrel assembly 24 supported thereby.

A sheet of material to be bent, indicated in the drawings by the letter B, is inserted between the mandrel assembly 2% and the draw sheet 49, the sheet material B being fed into position through one end of the machine. As illustrated in Figures 4 and 6 of the drawings the sheet material B will thus be engaged on its upper surface by the draw sheets 49 and by operation of the levers 36 the mandrel assemblies 24 are raised so as to engage the undersurface of the sheet material B. By any suitable means, such as through operation of the cylinders 65 the bending arms 43 are swung downwardly as illustrated in Figure 7 of the drawings, the material to be bent being wrapped about the mandrel plate 21 by the flex- 'ible draw sheet 49. At the start of the bend the springs 62 exert a relatively light pressure on the material to be bent. However, as the bending action continues the springs 62 are stretched to increase the tension on the draw sheet. This action takes place because of the relative positions of the center of pivot of the bending arms 63 and the center of curvature of the mandrel plate 21. Obviously the center of pivot of the arms 43 must be so arranged that the tension on the springs 62 increases as the arms bend downardl Dur ing the bending action the draw sheet 49 presses against the outer surface of the sheet being bent, thus preventing the fracture of fibers of iii) tion. This process requires considerable storage space for production work and it is necessary to store a twenty-four hours supply of material in liquid previous to the bending operation.

I have found that if composition material, such as Masonite, is soaked in a liquid which is heated to a temperature of approximately one hundred seventy-five degrees F. for about ten minutes, the sheets will absorb substantially eight percent of their dry weight of liquid, which will render the sheets sumciently pliable to permit bending thereof. The preferred range of temperature of the soaking liquid is from 149' F. to substantially F. Below 149 F. the-period required for the soaking of the material is considerably increased. Above 185 F. the surface of the fibrous material begins to separate so that a surface equal to that of the virgin material can not be maintained. I have also found that the period of time required for the soaking operation can be further decreased through the use of a wetting agent in the liquid which will allow the water to absorb into the composition more quickly.

Where extremely short radius bends are made in the composition, I may desire to remove a portion of the material on the inner surface of the bend so as to prevent buckling or weakening of the material. This I accomplish as illustrated in Figure 8 of, the drawings, by gouging out or removing a certain amount of the composition along the lines 76. This material may be removed by rotary saw blades or other gouging means which actually removes a portion of the material so that the remaining material can compress together under heat and pressurev at the point of the bend.

In accordance with the patent statutes, I have 4 prising a convex mandrel, a flexible draw sheet having one end fixedly secured in spaced relation to said mandrel, spring means secured to the other end of said draw sheet holding the same stretched taut and arranged to constantly exert a longitudinal pull on said other end of the draw sheet, and movably mounted means secured to the spring means and acting through the spring means to support said other end of the draw sheet and operable to wrap the draw sheet over the mandrel. I

2. A bending machine for sheet material comprising a body frame. a convex mandrel supported by said body frame, a flexible draw sheet secured at one end to said body frame in spaced relation to said mandrel, a bending frame means pivoted to said body frame to pivot with respect to said mandrel, and resilient means securing the other end of said draw sheet to said frame means and exerting a longitudinal pull on said other end of said draw sheet, said frame means, when pivoted, acting to wrap the draw sheet over said mandrel.

3. A bending machine for sheet material comprising a body frame, a mandrel supported thereby, a flexible draw sheet having one end anchored to said body frame in spaced relation to said mandrel and engageable against sheet material between said draw sheet and said mandrel to bend the sheet material over said mandrel, a frame means pivotally attached to said body frame and pivotal relative to said mandrel, and resilient means securing the other end of said draw sheet to said frame means and exerting a longitudinal pull upon said other end of said draw sheet, said mandrel being supported in the path of pivotal movement of said flexible draw sheet supported by said frame so that pivotal movement of the frame means bends the draw sheet, the bending of the draw sheet operating to 40 stretch'said resilient means as said draw sheet is engaged over said mandrel.

4. A bending machine for sheet material comprising a frame, a mandrel reciprocably mounted on said frame, a flexible draw sheet having 45 one endthereof anchored to said frame, said mandrel being reciprocable toward and away from said draw sheet, a bending frame pivoted to said frame, the other end of said draw sheet being resiliently secured to said bending frame, said bending frame operating, when pivoted, to wrap said draw sheet about said mandrel.

5. A bending machine for sheet material comprising a frame, a mandrel and a flexible draw sheet anchored at one end adjacent said man-' drel, said mandrel and draw sheet secured to and mounted on said frame for movement toward and away from each other, a bending frame pivoted to said frame, resilient means securing the other end of the draw sheet to said bending frame, said 0 bending frame, when pivoted, wrapping said draw sheet over said mandrel.

6. A bending machine for sheet material comprising a frame, a mandrel supported by said frame, a flexible draw sheet anchoredto said 65 frame adjacent said mandrel, said draw sheet and said mandrel being movable toward and away from one another, a clamping plate overlying said draw sheet designed to clamp said draw. sheet and asheet to be bent against said manasa'aeov drel, a bending frame pivoted to said frame, and means resiliently securing said draw sheet to said frame, the pivoting of said frame wrapping said draw sheet over said mandrel.

7. A bending machine comprising a mandrel, a flexible draw sheet anchored at one end adiacent said mandrel, said mandrel having a convex surface, a bending frame pivotedwith respect to said mandrel, resilient means connecting the other end of said draw sheet to said bending frame, the pivot of said frame being closer to the mandrel surface than the center of curvature of said mandrel so as to progressively stretch said resilient means as said bending frame is operated to wrap said draw sheet about said mandrel surface.

8. A bending machine comprising a mandrel, a flexible draw sheet anchored at one end in spaced relation to said mandrel, a bending frame pivoted with respect to said mandrel, a pair of opposed tracks on said bending frame, a carriage mounted for movement along said tracks secured to the other end of said draw sheet, and spring means urging said' carriage toward one end of said bending frame to stretch said draw sheet taut.

9. A bending machine comprising a mandrel, a flexible draw sheet anchored at one end in spaced relation to said mandrel, a bending frame pivoted withrespect to said mandrel, opposed tracks on said frame, a carriage on said tracks secured to the other end of said draw sheet, an adjustable support on the frame end, and spring means connecting said adjustable support to said draw sheet, the bending of said bending frame wrapping said draw sheet over said mandrel.

-10. A multiple bending machine comprising a pair of opposed mandrels, opposed draw sheets anchored at one end adjacent said mandrels in such a manner that a flat sheet may be positioned between said mandrels and said draw sheets, pivoted means for wrapping said draw sheets about said mandrels, and resilient means connecting said pivoted means to said draw sheets to continuously exert longitudinal pull thereupon.

11. The method of bending composition board on a convex mandrel with a flexible sheet anchored at one end adjacent said mandrel, the method consisting in placing the board on the mandrel, clamping the end of the board on one side of the mandrel in flxed position, and wrapping the flexible sheet about the mandrel, pressing the board toward themandrel with the flexible sheet engaging the board at the point of the bend, and exerting a constantly increasing longitudinal pull on the flexible sheet during the bending operation.

12. The method of bending composition board on a convex mandrel with a flexible sheet anchored at one end adjacent said mandrel, the method consisting in placing the board on the mandrel, clamping the end of the board on one side of the mandrel in fixed position, wrapping the flexible sheet about the mandrel, pressing the board toward the mandrel with the flexible sheet engaging the board at the point of bend, and gradually increasing the tension on the sheet during the bending operation.

WARREN H. NOBLES. 

